Transmitter



.im 9, 1945.. I v. MERRILL 2,386,705

TRANSMITTER Filed. June 18 1.941 2 Sheets-Sheet. l

` Q 7 lII///l/ff INVENTOR Laan/*ence ZV/carermli VL'VTNESSES fw a,

0% 9 1945? L v. MERRILL 2,386,705

TRANSMITTER Filed June 1s, 1941 2 sheets-sheet 2 AT TORNEYS TRANSME'ITER y Lawrence Victor Merrill, Brooklyn, N. Y., assgnor to Mears Radio Hearing Device Corp., New York, N. Y., a corporation of Delaware application .time 18, i941, sensi No. 398,528

2 claims. (n1. rio-107) IFais invention relates to improvements in devices which piel; up sound Waves, transform the waves into electric telephonie currents, and then amplify these currents to bring them up to sulcient strength for transmission to a suitable receiver for the benefit of deaf persons and those whose hearing is affected.

More particularly theinvention relates to a,de vice of the indicated character in which use is made of a microphone system and a vacuum-tube audio-amplifier system housed within a single casing of Suitable design.

Some of the objects and advantages of the invention are as follows. It provides a transmitter the type mentioned in which the parts are arranged in a compact relation in afford a device of correspondingly small size and of desirable shape capable of being carried about the person comfortably and inconspicuously. It provides a sound amplifying transmitter which is of eicient and substantial design and capable of giving a relatively high or low tone eiect of the desired volume. lt also provides for low frequenc control between the crystal and the first stage of ampliiication. unit is of such design as to afford extra space for certain parts of the amplifying system in such manner that a thinner over-all casing or one with less l .nay loe used.

The nature of the invention and its distinguishing features and advantages will appear when the following speciiication is read in connection with the accompanying drawings, in which l is an enlarged sectional View of a transembcdying the features of the invention, the section being taken approximately on the line lw-l oi 2 and looking in the direction indicated by the arrows;

Fig. 2 is an enlarged cross-section, the section being taken approximately on the line' 2-2 of l and looking in the direction indicated by arrows which both sections of the casing and parts associated therewith are shown;

Fig. 3 is a detail sectional view taken approxily on the line .3E-3 of Fig. l and looking in eci-.ion indicated by the arrows;

4l is a iront elevation of the transmitter a battery paci: shown partly in section in electrical connection with the transmitter;

5 is an inside view on an enlarged scale of the iront section or" the casing and showing the volume control rheostat;

6 wiring diagram of the microphone and audiowacuum :tube amplifying systems ac- The microphone or modulating. f

All

cording to the arrangement of elements shown in Figs. l and 2;

Fig. 7 is a wiring diagram in which one stage of amplication of the amplifying system has The casing l2 consists of two companion separf able sections, there being a back section i3 and a iront section lil. The casingsections may be composed of any suitable light weight insulatingrmaterial, such as hard rubber or Bakelite. The microphone system is in the form of a unit and includes a conical diaphragm i5. A metal ring it supports the diaphragm l5. The marginal edge portion of the diaphragm is glued, cemented, or otherwise secured to the ring. .A modulating element, such as a crystal ll, is connected with the apex of the diaphragm i5 for controlling or modulating the telephonie current in accordance with the frequency of the sound waves or impulses imposed on the diaphragm. The crystal is at and is of rectangular shape, preferably square. The crystal is secured to the ring by means of three curved members i3 integral with or secured, as at i9, to the ring and extending inwardly therefrom. The ends 2li of the members i3 are disposed parallel to the plane of the ring. Yieldable or resilient spacers 2i of rubber or similar material are disposed between the ends 2li, respectively, and the crystal lll and are secured by means of cement or paste to said ends and the front face of the crystal il. The members IB are connected to three corners, respectively, of the crystal il' and the fourth corner of the crystal is located substantially centrally of the casing l2 coincidental with the apex of the diaphragm l5 with which it is operatively connected. It Will therefore be understood that the parts l5 to 2l, inclusive, constitute a sound-responsive and modulating unit in which the crystal lies almost Wholly at one side of the apex of the diaphragm.

The amplifying system il includes a plurality ci miniature vacuum tubes 22, 23 and 2t. The tubes are preferably of the typewhich includes a plate, a grid, a filament, and a screen and are, therefore, each provided with ve terminals for connecting the same in the circuits of the amplifylng system in the usual manner for such systems as shown in Figs. 6 and 7. The tubes 22,

23 and 24 provide for a iirst, a second, and a third stage of amplification. The tubes are arranged around on the inside of the back section I3, disposed respectively in suitable recesses conforming to the shape of the tubes which are secured in place by a suitable adhesive or other means. The system il also includes various condensers 25, a biasing cell 2S. and a choke 2l. The cell 23 and choke 2l are arranged within the back section I3 in the space between the tubes 22 and 2li, whereas the condensers occupy the space beneath, beside, or around the crystal II and the other available space Within the section I3. The elements 2li, 23 and 2l are secured in place by suitable adhesive or other means within the section I3.

The sound responsive and modulating unit is resilicntly supported on the tubes and other elements in the section I3 by means of cushions or pads 23 of rubber, felt, or other suitable material, secured to these elements and also secured to the rear surface of the ring I6. It will be apparent assai-fcc erating on a high or a ,low tone frequency. The

that the crystal II is disposed well into the casing section I3 and that the members I8 ofthe ring are disposed between the crystal I'I and the ring I6, thereby making it possible to use-a casing which is thin or of relatively small bulk or depth.

The front casing section I 4 has opemngs 29 1n the central portion thereof .to allow the sound impulses to freely enter the casing to be impinged upon the diaphragm. In order to prevent leakage of sound around the diaphragm, there is provided a,-.ri.ng or gasket 3I of felt or other sound-absorbing material, which is secured to the portion 30 omi-.he inside thereof surrounding the springs 34 arranged in sockets respectively, there being ve of these sockets arranged in a row. The binding posts 32 and the springs 34 serve for the purpose of establishing electrical connections for rendering the amplifying system II fully operative. The portion 33 also has ve sockets 35, 35, 3l, 38 and 39, respectively, which open to the sockets containing the springs 34. The sockets 35, 36, 3l and 39 receive the terminal plugs, respectively, of a battery pack including an `A battery and a B battery and sockets for receiving the terminals of an extension cord connected with the usual crystal receiver R. The battery pack is illustrated in Fig, 4 and designated 40. The sockets 35, 31 and 39 receive from the plugs of the battery pack the electrical energy input, whereas the sockets 36, 31 and 38 complete the circuits to certain terminal plugs of the battery pack to furnish the sound output to the extension cord having the crystal receiver which the user applies to the ear in hearing with the device. The front casing section I4 on the central portion 30 carries a rheostat 4I with an operating knob 42 exteriorly of the section I4. The

rheostat 4I serves as a volume controLwhen ophaving a control knob 4d exteriorly of the section i3. This switch til is electrically connected with suitable resistances in a circut traversing the inn put circuit between the crystal Il and the first stage amplication tube 22. The knob 44 of the switch 43 may be turned to operate the vswitch i3 so as to eliminate low frequency impulses and thereby obtain clarity of tone. The rim of the casing section i3 also carries a switch 45 having a control knob 46 exteriorly of the section I 3. 'I'his switch is electrically connected with a suitable resistance andcondenser in a circuittraversing the output between the third stage amplifying tube 24 and the choke 2l. The knob 46 m'ay be manipulated to operate the switch 45 to eliminate high frequency impulses in order to assure clarity of tone.

The casing sections I3 and I4 are held in case- Aforming relationship by means of screw bolts 4l extending in holes in the section I3 and tapped holes in the section I4. This brings the ring I6 of the diaphragm in contactual engagement with the ring 3l -as explained hereinabove and the parts of the rheostat 4I on the inside of the sec-` tion I4 are conveniently received within the space aiorded by the conical diaphragm I5 as shown most clearly in Fig. 2.

In Fig. 6 is shown a wiring diagram of the amplifying circuits and elements appearing in Figs. 1, 2 and 5, For the sake of clearness the wiring has been omitted from said figures. In Fig. 7 there is shown a wiring diagram in which the 'second stage amplifying tube has been omitted and use has been made of an additional choke. 'I'his provision of elements may be conveniently arranged within the casing sections in which all of the advantages of the present invention may be attained.

I claim: l

1. A hearing device including a casing having sound openings therein, a, cushioning ring secured to the inside of said casing and surrounding said openings, a conical sound responsive diaphragm in contact along Iits marginal portion with said ring, a modulating element arranged within said casing, said portion having members resiliently connected with the front face of said element at spaced points to support the element, and a connection between the apex of the diaphragm and said front face of said element so that the latter willgenerate voltage in accordance with the irequency of the sound vibrations reaching the same from said diaphragm.

2. A device of the character described including a casing composed of separable front and back sections, a spider, means within the back casing section to resiliently support said spider, said spider having an annular portion adjacent the inner face of said front casing section, a diaphragm supported at the margin by said annular portion within said back section, a modulating element behind said diaphragm within said back section and connected with said diaphragm, and a gasket composed of yieldable sound absorbing material disposed between said front casing section and the margin of said diaphragm.

LAWRENCE VICTOR MERRILL. 

